Papers by Keyword: Nickel

Abstract: Carbon nanotubes (CNTs) are considered as the most promising materials to solve the electromagnetic interference (EMI) issue. Various forms of CNTs including CNTs/polymer composites, metal nanoparticles-decorated CNTs and freestanding CNT buckypapers (CNT BPs) have been proposed to enhance shielding effectiveness. In this study, the synergistic effect of nickel nanoparticles (NPs) and relatively short CNTs for the enhancement of microwave shielding properties was investigated. CNT BPs were prepared by vacuum filtration of well-dispersed multi-walled CNTs and subsequently nickel was decorated on the CNT BPs (Ni/CNT) by pulsed DC sputtering technique with different deposition times of 0, 5, 10 and 15 min (hereinafter referred to as CNi0, CNi05, CNi10 and CNi15, respectively). The diameter of Ni/CNT increased from 8.74±0.53 to 72.5±3.2 nm and the conductivity improved from 9.57±0.87 to 12.57±0.59 S/cm when the nickel deposition time was 15 min. Nickel NPs were the mixed phases of nickel and nickel oxide with a dominant nickel phase. The shielding effectiveness at the frequency of 9.5 GHz achieved to -34.1 dB for CNi15. The enhancement of shielding effectiveness of CNi15 is attributed to the synergistic effect of CNTs and nickel NPs on wave dissipation

Abstract: The current state of the issue of the slag waste processing was considered, using the example of the Southern Urals Nickel Plant. The average analysis of the chemical composition of the slag was performed; the determined phases contained iron, cobalt, nickel and chromium. The maps of the distribution of these elements in the slag were obtained.

Abstract: Steam turbine blades in the process of operation are subjects on which the high mechanical loads, erosion, corrosive and vibration effects. These factors significantly reduce their service life, which forces to costly repair work. The application of heat and wear-resistant coating on the turbine blades is a rational way to increase the service life of the turbine.

Abstract: Low specific contact resistivity and high-temperature reliability of the Ni (x)/Nb (100-x) (where x = 25, 50, 75 nm) ohmic contact to 4H-SiC were investigated. After the annealing process at 1000°C for 3 min in N₂ ambient, the I-V curves indicated that all the contacts exhibited the ohmic behaviors. Based on the transfer length method, the specific contact resistivity of the contacts were extracted. High concentration of Ni was responsible for low specific contact resistance of the Ni (75)/Nb (25)/4H-SiC sample by the formation of Ni₂Si compound after the fabrication process. However, this contact lost the ohmic behavior at low temperature of 150°C. Whereas, both Ni (50)/Nb (50)/4H-SiC and Ni (25)/Nb (75)/4H-SiC contacts remained the ohmic behavior for 100-hour aging at 400°C. Two-dimensional X-ray diffraction analyses showed that the presence of carbon agglomeration formed at the interface of the Ni (75)/Nb (25)/4H-SiC contact caused the degradation of this sample when being aged at high temperature environment. Meanwhile, higher concentration of Nb in the Ni (50)/Nb (50)/4H-SiC and Ni (25)/Nb (75)/4H-SiC samples improved the ability to collect the excess carbon atoms and thus enhanced the high temperature reliability of these contacts when operating in high temperature ambient. Considering both low specific contact resistivity and high temperature reliability, the Ni (50)/Nb (50)/4H-SiC contact can be a good candidate for harsh environment applications.

Abstract: This article represents the results of studies of the drawing thin wire from the alloy Pd-5Ni process. The studies used the software developed by the authors using the methods of calculating the drawing process and the computer model implemented in the DEFORM 3D software package. By way of calculation, a drawing route was determined, including 14 transitions, and the efforts of deforming the metal were found when producing wire with a diameter of 0.075. For this mode of deformation processing using the DEFORM 3D software package, we simulated the drawing process and established the temperature and stress distribution over the volume of the workpiece. The simulation results confirmed that the calculated safety factor for drawing is in the range of 2.85-3.43, which ensures a stable process of deformation of the metal without breaks and, as a consequence, an increase in productivity and yield of the suitable metal. Experimental studies have confirmed the adequacy of the developed model, so it can be used to analyze the process of drawing wire from other precious metal alloys. The results of the research are recommended to improve the production technology of thin wire from the alloy Pd-5Ni for the manufacture of catalytic gripping grids.

Abstract: The new ternary silicide Dy₃Ni_11.83(1)Si_3.98(1) was synthesized from the elements by arc-melting and its crystal structure was determined by X-ray single-crystal diffraction. The compound crystallizes in a Sc₃Ni₁₁Ge₄-type structure: Pearson symbol hP38, space group P6₃/mmc (No. 194), a = 8.1990(7), c = 8.6840(7) Å, Z = 2; R = 0.0222, wR = 0.0284 for 365 reflections. The structure belongs to a large family of structures related to the EuMg_5.2 type, with representatives among ternary aluminides, silicides, germanides, etc.

Abstract: The crystal structure of the (Cr,Ni)₄Si phase with and without Co was refined from X-ray powder diffraction data. The compound crystallises with an Au₄Al-type structure (Pearson symbol cP20, space group P2₁3): unit-cell parameter a = 0.611959(6) nm for the composition (Cr_0.312Ni_0.688)₄Si, a = 0.612094(6) nm for (Cr_0.375Ni_0.625)₄Si, and a = 0.612316(6) nm for (Cr_0.337Co_0.063Ni_0.600)₄Si. The magnetic susceptibility was measured in external fields up to 7 T at temperatures between 1.8 and 400 K. The three investigated samples exhibited paramagnetic behaviour described by the modified Curie-Weiss law: χ₀ = 146∙10^-6 emu g-at.^-1, μ_eff = 0.21 μ_B/atom, θ_P = -13 K for (Cr_0.312Ni_0.688)₄Si; χ₀ = 158∙10^-6 emu g-at.^-1, μ_eff = 0.20 μ_B/atom, θ_P = -15 K for (Cr_0.375Ni_0.625)₄Si; χ₀ = 169∙10^-6 emu g-at.^-1, μ_eff = 0.18 μ_B/atom, θ_P = -52 K for (Cr_0.337Co_0.063Ni_0.600)₄Si.

Abstract: The importance of the research is due to the lack of potable water (~1.6 million m³ per year) in a rapidly developing city in the Urals. One way to solve this problem is to purify water from the spent copper mine with a debit of ~4.4 million m³ of water per year. The most advanced techniques recently used for obtaining drinking water of a high quality are based on ion exchange and reverse osmosis, which can ensure an obtainment of water with initial contents of impurities much below the maximum permissible values. Based on the real experience the article compares sorption and membrane technologies in terms of water purification efficiency and cost of potable water production. The large-scale tests of mine water purification were carried out at sorption and reverse osmosis pilot plants with the capacity of 1 m³ per hour for the incoming flow. The source water had the following composition, mg/dm³: 0.5–0.9 Mn; 1.0–1.7 Ni; 80-140 Ca; 30-40 Na; 40-70 Mg; 0.2–0.6 Cu; 8.1–9.5 Si; 0.01–0.03 Zn; 0.01–1.70 Fe; <0.01 Al; < 0.005 As; < 0.005 Pb. At the same time the salinity was 640–680 mg/dm³, the water hardness was 9.5–11.5 mmol/dm³ and pH was 7.0-7.5. The content of non-mentioned impurities was below the detection limit. The resulting treated water met the requirements for the quality of potable water for both purification techniques. It was concluded, that the best option for treatment of mine water is ion exchange.

Abstract: The problem of processing slimes of galvanic production, formed as a result of neutralization of technological solutions and wastewater containing heavy non-ferrous metals is considered. At present, sludges are transported to disposal area and are not used in any way. Typically, such sludges contain significant amounts of chromium and nickel, which creates environmental hazard. Investigated sludge of Dimitrovgrad Automobile Units Plant (Russia) contains up to 6.6% Ni and up to 7,4% Cr. The hydrometallurgical process is proposed to treatment of these sludges. Solutions of sulfuric acid, ammoniaс chloride and Trilon B were used as lixiviants. It is shown that when using a solution of sulfuric acid with pH=1,5, extraction of up to 93,3% Cu, 70,2 Ni, 90,3 Zn is achieved.

Abstract: Through-pores alumina membranes of 50 μm thickness and 70 × 70 mm size have been fabricated to deposit Ni nanowires by electrochemical processing. Due to highly ordered microstructure of the membranes, the pores were filled by nanowires almost to 100%. The membrane nanowires composite morphology; structure and chemical features have been studied by scanning electron microscopy, atomic-force microscopy and X-ray structural analysis. To measure the specific magnetization σ as a function of temperature in the range of 77–1400 K, the pondero-motive method was used.